This invention relates to the production of glass in a continuous installation in which the different phases of the process, essentially melting, fining and conditioning, take place during a movement of the material through relatively delimited successive zones of the installation.
Means are described to improve the partitioning between said zones and in particular to regulate the flow of molten glass from one chamber to another. This increase in partitioning produces better control over each of the process phases.
The invention relates more particularly to tank furnaces with large production capacities, i.e., on the order of 600 t/d or more for float glass or 300 t/d for hollow glass. This invention also proves advantageous for smaller installations and especially where there are strict requirements with regard to the quality levels of the fining and/or chemical and thermal homogeneity of the glass which is to be supplied to the shaping devices.
The specific design and operation of the industrial installations vary. However, all installations attempt to separate and keep independent the melting process from the conditioning process.
Such independence and separation is obtained, for example, by connecting the melt tank to the conditioning tank by a submerged throat. As a result the two compartments are not exposed to either to the outside atmosphere or to each other's atmosphere. The throat is a common structure used in installations that produce hollow glass and installation fiber.
In contrast, glass furnaces that produce flat glass with high production capacities usually contain a neck that connects the melting and cooling-down compartments. The neck is a section whose crown is not in contact with the glass bath.
Utilization of a throat offers certain advantages over that of a neck. The throat guarantees the independence of the atmospheres of the two compartments. This favors the production of glass from the melting tanks which exhibit a better fining quality and/or is colder since it is located closer to the bottom of the bath. However, since the section of the throat is limited in practice by the maximum dimensions of the pieces of the crown which the refractory industry is currently able to produce, the throat is only able to be used in furnaces whose pull does not exceed about 200 t/d.
Therefore, tank furnaces in the flat-glass industry, whose production capacity exceeds over 600 t/d cannot use the preferred throat section but rather must resort to using a section called a neck. An extension of the tank is used to remedy some of the drawbacks that occur with regard to the quality of the glass produced as a result of using a tank furnace which comprises a neck as opposed to a throat. This extension is devoted to the conditioning process and creates a strong longitudinal convection belt with a surface current and a bottom current. The surface current is five to ten times the pull, and is directed downstream, reaching the extraction zone after having passed previously through both the neck and the conditioning tank. The bottom current of the convection belt, which is only reduced by the pull, travels the opposite path.
These convection currents subject the refractory pieces that constitute the neck to considerable wear and thus shorten their life. The convection currents also prove very costly in terms of energy loss. They involve several thermal cycles of cooling and heating of the glass between the fining and cooling-down temperatures prior to the glass being removed for shaping. It is the object of the present invention to remedy, or at least reduce substantially, the drawbacks of each of the structures described above.